1. Technical Field
The present invention relates to a sound analysis apparatus and a sound analysis program that determine whether a performance sound is generated at a pitch as designated by a musical note or the like.
2. Background Art
Various types of musical instruments having a performance self-teaching function have been provided in the past. Keyboard instruments are taken for instance. This type of musical instrument having the self-teaching function guides a user (player) to a key to be depressed by means of display or the like on a display device, senses a key depressed by the user, informs the user of whether a correct key has been depressed, and prompts the user to teach himself/herself a keyboard performance. For realization of the self-teaching function, a key depressed by a user has to be sensed. This poses a problem in that a keyboard instrument without a key scan mechanism cannot be provided with the self-teaching function.
Consequently, a proposal has been made of a technology for collecting a performance sound, analyzing the frequency of the sound, and deciding whether a performance sound having a correct pitch designated by a musical note has been generated. For example, according to a technology disclosed in a patent document 1, various piano sounds of different pitches are collected, the frequencies of the collected sounds are analyzed, and a power spectrum of a piano sound of each pitch is obtained and stored in advance. When a piano performance is given, a performance sound is collected, and the frequency of the sound is analyzed in order to obtain a power spectrum. Similarities of the power spectrum of the performance sound to the power spectra of various piano sounds of different pitches that are stored in advance are obtained. Based on the degrees of similarities, a decision is made on whether the performance has been conducted as prescribed by the musical notes.
[Patent Document 1] JP-A-2004-341026
[Patent Document 2] Japanese Patent No. 3413634
[Non-patent Document 1] “Real-time Musical Scene Description System: overall idea and expansion of a pitch estimation technique” (by Masataka Goto, Information Processing Society of Japan, Special Interest Group on Music and Computer, Study report 2000-MUS-37-2, Vol. 2000, No. 94, pp. 9-16, Oct. 16, 2000)
However, the power spectrum of an instrumental sound has overtone components at many frequency positions. The ratio of each overtone component is diverse. When there are two instrumental sounds to be compared with each other, although their fundamental frequencies are different from each other, the shapes of their power spectra may resemble. Consequently, according to the technology in the patent document 1, when a performance sound of a certain fundamental frequency is collected, a piano sound whose fundamental frequency is different from the fundamental frequency of the collected performance sound but whose power spectrum resembles in shape with the power spectrum of the collected performance sound might be inadvertently selected. This poses a problem in that the pitch of the collected performance sound may be incorrectly decided. Moreover, according to the technology in the patent document 1, since the fundamental frequency of a collected performance sound is not obtained, an error in a musical performance cannot be pointed out in such a manner that a sound which should have a certain pitch is played at another pitch.